Flow control system for an aircraft

ABSTRACT

A method for providing a flow control system for an aircraft. A compressor is removed from an existing air cycle machine, along with compressor ducting that is connected to a primary stage outlet of the heat exchanger and a secondary stage inlet of the heat exchanger in the existing air cycle machine. A first connector duct is provided and connected to the primary stage outlet of the heat exchanger and the secondary stage inlet of the heat exchanger. The turbine is removed from the existing air cycle machine, and a second connector duct is provided and connected to the upstream turbine duct directly and the downstream turbine duct.

FIELD OF THE INVENTION

The present invention relates to the field of environmental controlsystems for aircraft and, more particularly, to a flow control systemand a method for converting an existing air cycle system into a flowcontrol system.

BACKGROUND OF THE INVENTION

Commercial aircraft typically include environmental control systems thatregulate air supply, temperature, and cabin pressurization on theaircraft. Such environmental control systems may also be utilized toprovide cooling to components of the aircraft itself, such as electricalsystems. The environmental control system of most jet aircraft typicallyincludes two or more air cycle machine cooling devices, which providepressurized air of an appropriate temperature to the cabin of theaircraft by utilizing heated, pressurized bleed air from the jet enginesor auxiliary power unit of the aircraft, as well as ram air, which isambient air that enters the aircraft through a ram scoop.

A typical air cycle machine includes a turbine that is mechanicallyconnected to a compressor, such that the turbine provides a rotationalforce to the compressor in order to operate the compressor. The turbineand compressor are selectively operable and cooperate to reduce thetemperature of the bleed air to allow cooling of the aircraft. However,a typical air cycle machine also includes a heat exchanger that coolsthe bleed air using the ram air. When the aircraft is in flight, theambient air temperature is so low that operation of the turbine andcompressor is not needed to cool the bleed air, and thus, the turbineand compressor air typically only operate when the aircraft is flying atlow altitude or on the ground.

While the air cycle machines are well-suited to conditioning andpressurizing air both while the airplane is on the ground and while theairplane is in flight, the air cycle machines are heavy, and the addedweight that must be carried by the aircraft causes an increase in fuelconsumption. Furthermore, in applications where passengers are not beingtransported by the aircraft, the presence of redundant air cyclemachines on the aircraft is unnecessary, and simultaneous operation ofthese redundant systems further increases fuel consumption. Accordingly,it would be desirable to have an environmental control system for anaircraft that was of reduced weight and complexity.

SUMMARY OF THE INVENTION

The invention provides a method for providing a flow control system foran aircraft by converting an existing air cycle machine on the aircraft.The existing air cycle machine includes a heat exchanger with a primarystage and a secondary stage, a compressor that is connected to the heatexchanger by a compressor ducting section, a turbine that is connectedto the heat exchanger by an upstream turbine duct, and a downstreamturbine duct that is connected to the turbine.

The method comprises the steps of removing the compressor, removing thecompressor ducting from a primary stage outlet of the heat exchanger anda secondary stage inlet of the heat exchanger, providing a firstconnector duct, connecting the primary stage outlet of the heatexchanger to the first connector duct, and connecting the secondarystage inlet of the heat exchanger to the connector duct such that airmay travel from the primary stage of the heat exchanger directly to thesecondary stage inlet of the heat exchanger by way of the firstconnector duct. The method also comprises the steps of removing theturbine, providing a second connector duct, and connecting the upstreamturbine duct directly to the downstream turbine duct using the secondconnector duct.

The method may further include the steps of providing the air cyclemachine having a bypass valve disposed in the upstream turbine duct,wherein the bypass valve is electrically connected to a control systemto provide operating signals thereto, providing the air cycle machinehaving a bypass duct connected to the upstream turbine duct and thedownstream turbine duct, wherein the bypass valve selectively directsair to the turbine or through the bypass duct, removing the bypass valvefrom the upstream turbine duct, and providing a third connector duct,replacing the bypass valve with the third connector duct. The method mayfurther include the steps of disconnecting the electrical connectionbetween the bypass valve and the control system, providing a valvefeedback unit operable to provide operating signals to the controlsystem, and electrically connecting the valve feedback unit to thecontrol system.

Additionally, the valve feedback may be configured to provide operatingsignals that emulate the operating signals provided by the bypass valveto the control system prior to the step of disconnecting the electricalconnection between the bypass valve and the control system.

The method may further include the steps of providing the air cyclemachine having a water separator connected to a primary stage outlet ofthe heat exchanger and to a system outlet duct and replacing the waterseparator with a fourth connector duct. The method may also include thesteps of providing the air cycle machine having the system outletconnected to a mixing manifold and providing the air cycle machinehaving at least one auxiliary air cycle machine connected to the mixingmanifold.

The invention also provides an environmental control system for anaircraft that includes a bleed air source that is connected to at leasta first air cycle machine and at least a first flow control system. Theair cycle machine that has an air cycle inlet that is connected to thebleed air source and is operable to provide conditioned air to an aircycle outlet. The flow control system has a flow control inlet that isconnected to the bleed air source and is operable to provide cooled airto a flow control outlet. The cooled air is produced by the flow controlsystem may be produced solely by heat exchange. A mixing manifoldreceives conditioned air from the air cycle machine and cooled air fromthe flow control system and is operable to selectively provide thecooled air, the conditioned air, or mixed air to the aircraft. Themixing manifold produces the mixed air by mixing the cooled air and theconditioned air. The air cycle machine may include at least oneturbine-compressor pair to produce conditioned air.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawings,wherein like-referenced numerals refer to like parts throughout severalviews and wherein:

FIG. 1 is a block diagram showing a conventional air cycle machine of anaircraft;

FIG. 2 is a block diagram showing a flow control system of an aircraftaccording to the present invention;

FIG. 3 is an illustration of an existing air cycle machine of anaircraft prior to modification according to the method of the presentinvention;

FIG. 4 is a diagram showing a flow control system of an aircraftfabricated by modifying the existing air cycle machine of the aircraftof FIG. 3 according to the method of the present invention.

FIG. 5 a is a first exemplary embodiment of an environmental controlsystem for an aircraft according to the present invention;

FIG. 5 b is a second exemplary embodiment of an environmental controlsystem for an aircraft according to the present invention; and

FIG. 5 c is a third exemplary embodiment of an environmental controlsystem for an aircraft according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, the present invention will now be describedin detail with reference to the disclosed embodiment.

FIG. 1 shows a conventional air cycle machine 10, which is used toprovide a fresh air supply, temperature control, and cabinpressurization in an aircraft (not shown). The air cycle machine 10includes a bleed air inlet 12, which is typically connected to a sourceof heated, pressurized air, such as a bleed air port (not shown) that isprovided in a compressor stage of one of the engines (not shown) of theaircraft. A flow control valve 14 is disposed downstream of the inlet 12to control the quantity of bleed air introduced into the air cyclemachine 10.

In order to cool the bleed air, the air cycle machine 10 includes a heatexchanger 15. The heat exchanger 15 has a primary stage 16 and asecondary stage 24. Cooling of the bleed air in the heat exchanger 15 isprovided by a ram air stream 18. The ram air stream 18 enters theaircraft through a ram air scoop 20 and travels through the primarystage 16 of the heat exchanger 15 as well as the secondary stage 24 ofthe heat exchanger 15 before exiting the aircraft through a ram airoutlet 22.

The bleed air enters the primary stage 16 of a heat exchanger 15 at aprimary stage inlet 17 a downstream of the flow control valve 14. Thebleed air is then cooled by the ram air stream 18 in the primary stagebefore exiting the heat exchanger 15 at a primary stage outlet 17 b.Downstream of the primary stage 16 of the heat exchanger 15, the bleedair reaches a first junction 26, where the bleed air may either proceedthrough a one-way check valve 28 or through a compressor 30.

If the compressor 30 is operating, air is directed from the firstjunction 26 through the compressor 30 due to the low pressure conditionpresent at the inlet of the compressor 30 when it is operating, and airis prevented from returning to the first junction 26 from thehigh-pressure outlet of the compressor 30 by the check valve 28. In thecompressor 30, the bleed air is compressed, thereby pressurizing andheating the bleed air. If the compressor 30 is not operating, themajority of the bleed air proceeds through the check valve 28, ratherthan past the non-operating compressor 30, as the bleed air travelingthrough the check valve 28 offers less resistance. However, a portion ofthe bleed air travels through the non-operating compressor 30, reducingthe overall efficiency of the air cycle machine 10.

Downstream of both the check valve 28 and the compressor 30 is a secondjunction 32, where the bleed air streams from the check valve 28 and thecompressor 30 to rejoin one another before entering the secondary stage24 of the heat exchanger 15 at a secondary stage inlet 25 a. In thesecondary stage 24 of the heat exchanger 15, the bleed air is againcooled by the ram air stream 18 before exiting the heat exchanger 15 ata secondary stage outlet 25 b.

Downstream of the secondary stage 24 of the heat exchanger 15, the bleedair reaches a third junction 34, where the air may proceed either to abypass valve 36 or to a turbine 38 that is mechanically connected to thecompressor 30. If the bypass valve 36 is open, the majority of the airproceeds through the bypass valve 36, as doing so offers less resistancethan traveling through the turbine 38. However, some of the bleed airmay still travel through the turbine 38 while the bypass valve 36 isopen, but this amount of bleed air will not cause operation of theturbine 38. The bleed air then proceeds to a water separator 40 and thento an outlet 42. If the bypass valve 36 is closed, air proceeds throughthe turbine 38, causing rotation of the turbine, which expands and coolsthe bleed air. The bleed air then proceeds from the turbine 38 to thewater separator 40 and the outlet 42.

In order to regulate operation of the air cycle machine 10, a controlsystem 44 is electrically connected to the flow control valve 14 to varythe amount of bleed air received from the inlet 12. The control system44 is also electrically connected to the bypass valve 36 to selectivelyoperate or bypass the turbine 38.

FIG. 2 shows a flow control system 100 according to the presentinvention. As described in connection with the air cycle machine 10,heated, pressurized bleed air is received at the inlet 12, and the flowcontrol valve 14 is configured to vary the amount of bleed air providedto the primary stage 16 of the heat exchanger 15. The bleed air thenenters the primary stage 16 of the heat exchanger 15 at the primarystage inlet 17 a, where the bleed air is cooled by the ram air stream 18before exiting the heat exchanger 15 at the primary stage outlet 17 b.

After leaving the primary stage 16 of the heat exchanger 15, the bleedair continues directly to the secondary stage 24 of the heat exchanger15 by way of the secondary stage inlet 25 a. The connection between theprimary stage 16 of the heat exchanger 15 and the secondary stage 24 ofthe heat exchanger 15 is direct without junctions or valves, therebypreventing inefficiencies in the flow control system.

In the secondary stage 24 of the heat exchanger 15, the bleed air isagain cooled by the ram air stream 18 before exiting the heat exchangerat the secondary stage outlet 25 b. After leaving the secondary stage 24of the heat exchanger 15, the bleed air proceeds to the outlet 42, whichis directly connected to the secondary stage 24 of the heat exchanger 15without intervening valves or junctions.

In order to regulate operation of the flow control system 100, thecontrol system 44 is electrically connected to the flow control valve14, as well as a valve feedback unit 46. The control system 44 regulatesoperation of the flow control valve 14 to control the amount of bleedair introduced into the aircraft by way of the inlet 12. Because thecontrol system 44 is configured such that it expects to receive signalsfrom a bypass valve such as the bypass valve 36 of the air cycle machine10, the flow control system 100 includes a valve feedback unit 46. Thevalve feedback unit 46 does not include nor is associated with an actualvalve that controls an aspect of flow of air through the flow controlsystem 100. Rather, the valve feedback unit 46 is an electricalapparatus configured to emulate the electrical signals that would beoutput by the bypass valve 36 of the air cycle machine 10 withoutcausing corresponding changes in the operation of the flow controlsystem 100.

In a method according to the present invention, the air cycle machine 10can be modified to provide the flow control system 100. As shown in FIG.3, the air cycle machine 10 includes a compressor ducting section 50that is connected to the primary stage outlet 17 b and the secondarystage inlet 25 a of the heat exchanger 15. The compressor ductingsection 50 transports air from the primary stage 16 of the heatexchanger 15 to the secondary stage 24 of the heat exchanger 15 by wayof the one-way check valve 28 of the compressor 30 if the compressor 30is in operation. Thus, the compressor ducting section 50 includes thefirst junction 26, the one-way check valve 28, the compressor 30, thesecond junction 32, and the necessary piping to interconnect theseelements with the heat exchanger 15. The air cycle machine 10 furtherincludes an upstream bypass duct 52 that extends from the third junction34 to the turbine 38, an upstream turbine duct 54 that extends form thebypass valve 36 to the fourth junction 39, and a downstream turbine duct56 that extends from the fourth junction 39 to the water separator 40.

In order to direct air from the outlet side of the primary stage 16 ofthe heat exchanger 15 to the secondary stage 24 of the heat exchanger15, the compressor 30 and the compressor ducting section 50 are removed.A first connector duct 58 is provided to replace the compressor 30 andthe compressor ducting section 50, as shown in FIG. 4, and is thusconnected to both the primary stage outlet 17 b of the heat exchanger 15as well as the secondary stage inlet 25 a of the heat exchanger 15. Thefirst connector duct 58 may be substantially continuous, thereby lackingjunctions or valves that would impede air flow.

Next, the turbine 38 is disconnected from the upstream bypass duct 52,the upstream turbine duct 54, and the downstream turbine duct 56, andthe turbine 38 is removed. In order to replace the turbine 38, a secondconnector duct 60 is provided. The second connector duct 60 is connectedto the upstream turbine duct 54 and the downstream turbine duct 56.Then, the bypass valve 36 and the water separator 40 are removed andreplaced with a third connector duct 62 and a fourth connector duct 64,respectively, since removal of the compressor 30 and the turbine 38 hasrendered them unnecessary. Remaining unused duct openings, including theupstream bypass duct 52, are sealed using caps 66. In order to replicatethe electrical signals previously transmitted to the control system bythe bypass valve 36, and thus avoid the need for modification to thecontrol system 44, the valve feedback unit 46 is electrically connectedto the control system 44.

The flow control system 100 may be incorporated into an aircraft invarious ways, as shown in FIGS. 5 a-5 c. For example, in a firstexemplary environmental control system 200, the bleed air source 12 isconnected to one air cycle machine 10 and two flow control systems 100.Alternatively, a second exemplary environmental control system 202includes a pair of air cycle machines 10 and a single flow controlsystem 100. As a further alternative, a third exemplary environmentalcontrol system 204 includes a single air cycle machine and a single flowcontrol system. In each case, the air cycle machines 10 and the flowcontrol systems 100 are interconnected by manifolds (not shown) thatdeliver air to the air cycle machines 10 and the flow control systems100, as well as mix the air received from the air cycle machines 10 andthe flow control systems 100.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but to the contrary, it is intended to covervarious modifications or equivalent arrangements included within thespirit and scope of the appended claims. The scope is to be accorded thebroadest interpretation so as to encompass all such modifications andequivalent structures as is permitted under the law.

1. A method for providing a flow control system for an aircraft byconverting an air cycle machine on the aircraft having a heat exchangerwith a primary stage and a secondary stage, a compressor connected tothe heat exchanger by a compressor ducting section, a turbine connectedto the heat exchanger by an upstream turbine duct, and a downstreamturbine duct connected to the turbine, the method comprising the stepsof: removing the compressor; removing the compressor ducting from aprimary stage outlet of the heat exchanger and a secondary stage inletof the heat exchanger; providing a first connector duct; connecting theprimary stage outlet of the heat exchanger to the first connector duct;connecting the secondary stage inlet of the heat exchanger to theconnector duct such that air may travel from the primary stage of theheat exchanger directly to the secondary stage inlet of the heatexchanger by way of the first connector duct; removing the turbine;providing a second connector duct; and connecting the upstream turbineduct directly to the downstream turbine duct using the second connectorduct.
 2. The method stated in claim 1, the steps further comprising:providing the air cycle machine having a bypass valve disposed in theupstream turbine duct, wherein the bypass valve is electricallyconnected to a control system to provide operating signals thereto;providing the air cycle machine having a bypass duct connected to theupstream turbine duct and the downstream turbine duct, wherein thebypass valve selectively directs air to the turbine or through thebypass duct; removing the bypass valve from the upstream turbine duct;providing a third connector duct; and replacing the bypass valve withthe third connector duct.
 3. The method stated in claim 2, the stepsfurther comprising: disconnecting the electrical connection between thebypass valve and the control system; providing a valve feedback unitoperable to provide operating signals to the control system; andelectrically connecting the valve feedback unit to the control system.4. The method stated in claim 3, wherein the valve feedback unit isconfigured to provide operating signals that emulate the operatingsignals provided by the bypass valve to the control system prior to thestep of disconnecting the electrical connection between the bypass valveand the control system.
 5. The method stated in claim 1, the stepsfurther comprising: providing the air cycle machine having a waterseparator connected to a primary stage outlet of the heat exchanger andto a system outlet duct; and replacing the water separator with a fourthconnector duct.
 6. The method stated in claim 5, the steps furthercomprising: providing the air cycle machine having the system outletconnected to a mixing manifold; and providing the air cycle machinehaving at least one auxiliary air cycle machine connected to the mixingmanifold.